Method of selectively dyeing and etching anodized aluminum

ABSTRACT

This method involves etching of parts, except for portions corresponding to desired figures, by steeping the parts in etching solution after anodic oxidation of aluminium and printing figures on its surface. This is very useful in presenting colored relief figures on the surface of aluminium and forming figure patterns of aluminium on the surface of acid- and alkali-proof materials.

United States Patent [72] lnventor Masanori lzumikawa Urawa-shi, Japan [2 l] Appl. No. 811,369

[22] Filed Mar. 28, 1969 [45] Patented Nov. 23, 1971 [73] Assignee Yoshitaka Katayama Tokyo, Japan [32] Priority Mar. 14, 1969 [33] Japan [54] METHOD OF SELECTIVELY DYEING AND ETCHING ANODIZED ALUMINUM 7 Claims, 2 Drawing Figs.

[52] [1.8. CI 204/35 N, 204/5 8 [5l Int. Cl C23f 5/04 [50] Field of Search 204/33, 35,

Primary Examiner-John H. Mack Assistant Examiner-W. 1. Solomon A!!0rneyJecies and Grenside ABSTRACT: This method involves etching of parts, except for portions corresponding to desired figures, by steeping the parts in etching solution after anodic oxidation of aluminium and printing figures on its surface. This is very useful in presenting colored relief figures on the surface of aluminium and forming figure patterns of aluminium on the surface of acidand alkali-proof materials.

1-]. Anodic O Oxide Coating Formation Elimination of ZI-Ll-Z water washing I l I Anhydration Hl-B Drying [1 Printing I-Ilflowment of Ink I 1-5 Drying Appearance of Colored Fi ures Elimination 01 I L Disused Oxide Coating 1 6 Etching Appearance of I Relief Figures Elimination of 1- w ter iashi 1 Etching Solut1oriI i a I g Elimination of Residual Etchin Solution 1-8 Neutralization Elimination of I w I Counter-agent l 9 water ashing 1-10 Anodic xide Coating Reoxidation Formation Elimination of 1 w w I L E ec Y I-Il l ater ashing 1-12 l-lole Sealing Elimination of Vehio1esH:-3 Vehicle Solution Elimination of SolvenTHLh water washing] 1-15 Hole Sealing PATENTEDuuv 23 I9?! SHEET 1 BF 2 l-l Anodic Oxidation Elimination giectrolyte 1-2 Water washing Anhydration 1-3 Drying 1 Printing Appenrancr: of

Disused Oxide Coating l 1'5 Drylng Colored F1 ur s 1 Elimination of F4 Etching Appearance of 521.! QELEPELJLEE 1-7 Water Washi n1;

Elimination of Residual Etching Solution l-8 Neutrallxation Elimination of Counter-agent 1-9 water Washing l-lO Anodic 0Xide Coating Reoxidation Formation Elimination Of L 1 1 w, t r w }j Electrolyte d 6 d8 Q l -l2 Hole Sealing v l Elimination of Vehicles vehicle Solution I Elimination of Solvent l-lh- Water Washing Hole Sealing PATENTEU NOV 2 3 I971 SHEET 2 UF 2 2-l Plastering of Endowmr'nt of laterials Binding Agent 2-2 Anodic Oxide Coating Oxidation Formation Elimination of Electrolyte 2 3 water Washing Anhydration 2- Drying 2-5 Printing Endomment of Ink .ppearance of 2 6 Drying Colored Figures Elimination of a Figure Patterns Disused Aluminium 2 7 Etching Formation Elimination of Etching Solution 2-8 water Washing Elimination of Residual Etching SolutiQ l 2-9 Neutralization Elimination of Counter-agent 2-10 water Washing 2-ll Vehicle v Solution Elimination of Solvent 2-12 water washing 2-13 Hole Sealing METHOD OF SELECTIVELY DYEING AND ETCI'IING ANODIZED ALUMINUM BACKGROUND OF THE INVENTION This invention relates to a method of aluminum processing, and more especially to' a method of aluminum processing suitable for presentation of figures on the surface of aluminum and formation of aluminum figure patterns on the surface of acidand alkali-proof materials.

Anodic oxidation film of aluminum has dyeability, because colors are absorbed by pinholes of the film; it is a peculiar feature of aluminum which is not seen in other metals. When colored figures are to be provided on the surface of aluminum use is made of this dyeability of anodic oxidation film, which is known from Japan Pat. No. 225385. But by this method, even if microscopic, it is not possible, of course, to form relief figures. It is well known that by applying protective coatings to the anodic oxidation film of aluminum and steeping the film in alkali solution such as diluted sodium hydroxide to etch the anodic oxidation film except the said protective coatings, the relief figures of anodic oxidation film under the coating part on the surface of the aluminum can be presented. Concerning this, Japan Pat. No. 275033 reports that if aluminum is reanodic-oxidized after etching by a different electrolyte from the first one, the surface of aluminum can be provided with more than two colors at the same time. However at any rate the figure can be formed so that it is embossed by these methods, but to color the above figures at will cannot be expected; for only the color tones of anodic oxidation film itself can be obtained. As a matter of fact, a simple way or concrete method suited for presenting colored relief figures on the surface of aluminum is not well known until now.

On the other hand, the method of printing figures on aluminum foils and cutting them out to stick the figure patterns is widely used for making ornaments, for example, for mold goods of synthetic resin and glass, because aluminum itself has an attractive color tone, and it is a pretty inexpensive and easily workable material. This method involves the application of cutouts to the surfaces of mold goods and sheetlike materials such as paper and fiber. But to cut out some desirable figure patterns from aluminum foils is very difficult, except when the drawings of the figures are simple and clear; therefore it is impossible to present such subtle figures as in photos or ambiguous figures; This is because in most cases the economics of manufacturerequire stamping out of the figure patterns by a press. In addition, at the same time, the method has a fault in that the figure pattern has a uniform thickness and does not give an impression of relief to the figure; furthermore in adhering the figure patterns the work involved in arranging them presents some difficult problems.

The general object of this invention is to provide a method of aluminum processing by which it is possible to provide colored figures on the surface of an aluminum article and to etch the article or part except for the figures.

Another object of this invention is to provide a method of aluminum processing by which not only colored figures may be provided but also relief figures which fit exactly the colored figures on the surface of an aluminum article.

A further object of this invention is to provide a method of aluminum processing by which colored figure patterns can be formed on the surface of a material, if the material has a small amount of acidand alkali-proof surface.

A still further object of this invention is to provide a method of aluminum processing which is easily operated and has the possibility of mass-production as well as being quite inexpenstve.

SUMMARY OF THE INVENTION This invention involves the following consideration: in providing colored figures on aluminum, the ink contains a vehicle which is chemically stable, as well as oil colors, and in making it into an anodic oxidation film of the above-mentioned aluminum it is separated into the vehicle and the oil colors, which settle into pinholes of the above-mentioned anodic oxidation film, as the result the vehicle remains on the film surface; consequently if one can dye colored figures on the anodic oxidation film and etch the film except for the figures, it will be possible to obtain not only colored figures but also relief figures which correspond exactly to the colored figures on the surface of the aluminum; and in this case, if the aluminum is a foil and it is stuck on the surface of acidand alkali-proof materials, it will be possible to form the figure patterns in accordance with the colored figures of aluminum on the surface of the said materials by prolonging the etching time or reetching and removing the foil itself as well as the anodic oxidation film except the colored figures. According to my invention, the vehicle in the ink has a different density from the oil colors, and the vehicle is alkaliand acid-proof in order to be able to bear etching and chemical treatment thereafter. In many cases, etching itself is made in alkali-solution, but in the chemical process thereafter (for example neutralization, re-anodic-oxidizing) it is steeped in acid-solution; therefore it is necessary, as above-mentioned, for the vehicle to be acid-proof as well as alkali-proof. For these requirements, the vehicle in the ink consists of materials of which chief elements are rubber or synthetic resin. The vehicle has a lesser density than oil colors and is alkaliand acidproof chemically. Further in formation of aluminum figure patterns on the surface of a material, the material should be acid and alkali-proof, because it is steeped in electrolyte and etching solution with aluminum. In this case, it is not necessary for the material itself to be essentially acidand alkaliproof; it is enough that its surface has the above-mentioned properties. Therefore the application to synthetic resins, glass and fiber is the most common, but one can apply the invention to a material which is surface-coated with synthetic resin though it is not acidand alkali-proof.

The feature of this invention is that in aluminum processing the ink which is added to the anodic oxidation film does the part of masking against etching the anodic oxidation film except the figures as well as dyeing the figures on the film. In other words it is to provide dyeing affinity for the masking body itself. It is well known that in coating what is called masking" is the operation to stick what is not easily acted upon by the colors and is easily removable thereafter, on the part where coating is not necessary. This is widely known in the field of aluminum. According to the concept of masking up to date, it aims at the protection of present conditions against the process or operation after masking; at any rateit means preventing change from that condition. Beyond such conventional concept, this invention has given the ink two properties of a coloring matter for dyeing and a masking body for etching.

As a summary: This invention is a method of aluminum processing, where figures are printed or painted on the abovementioned anodic oxidation film of aluminum, using an ink in which oil colors are dispersed in an alkaliand acid-proof vehicle, and thereafter the anodic oxidation film is etched except for the figures, by steeping the aluminum in etching solu- -tion such as diluted caustic soda, to present colored and relief figures on the surface of the aluminum; and further it is a method of aluminum; processing where aluminum foils are adhered to the surface of acidand alkali-proof material, and anodic oxidation film is formed on the surface of this aluminum, then desired figures are printed or painted in ink in which oil colors are dispersed in the alkaliand acid-proof vehicle, and,then the aluminum foils are removed except for the figures by steeping the above aluminum in etching solution such as diluted caustic soda to form figure patterns of aluminum on the surface of the material in accordance with the desired colored figures.

As a matter of fact, the vehicle in the ink is, as above-mentioned, composed of materials of which main elements are rubber or synthetic resins-in most cases chlorinated rubber or acrylic and epoxy resin. But if necessary, some other materials which are alkaliand acid-proof, and have properties suited for the vehicle, will suffice--e.g., natural resins such as pine resin. At any rate, it is desirable that the vehicle itself be colorless, but a white one is sufiicient. If chlorinated rubber is used the preparing process is to make a mixture, for example, of chlorinated rubber, chlorinated paraffin, gelvarnish, drying-inhibiter and solvent as a nucleus, then to add to it oil colors dissolved in such a solvent as nitrobenzol, and then to heat and stir the mixture. When the mixture is used in practice, varnish, reducer or linseed oil is added to it to arrange its viscosity.

In case of using synthetic resins, the preparing process is almost the same, though the materials are different. In addition, to give full play to the features of this invention it is desirable to bear in mind the components of the ink and their ratios, viscosity and drying velocity, but in many cases the best valuation for each color is decided by its way of use; namely, practical way of printing.

BRIEF DESCRIPTION OF THE DRAWINGS Frorn hereon I will explain the concrete examples of my invention in the figures.

FIG. I is a flow sheet illustrating the process of presenting figures on the surface of aluminum by this invention; and

FIG. 2 is a flow sheet illustrating the process of forming aluminum figure patterns on the surface of acidand alkaliproof material by this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Example I: In case of presenting figures on the surface of aluminum) (See FIG. 1.) I-l. Fonnation of Anodic Oxidation Film Anodic oxidation film comprising pinholes which is able to absorb oil colors is formed on the surface of aluminum. In this case, percent sulfuric acid is the desirable amount as electrolyte, and the electrolytic conditions are:

Current Classification DC Current Density 0.5 A/cm. Voltage 12-15 v. Solution Temperature C.

Time 45-60 mins.

l-2. Washing out Electrolyte Being treated for a minute or two in running water. I-3. Dehydration Both natural drying and thermal drying will do, but it is more advantageous to the following work if the temperature of the aluminum can be kept at 20-30 C. l-4. Printing Figures Desired figures are printed on the anodic oxidation film of aluminum, using the ink dispersed with oil colors in an acidand alkaliproof vehicle. In this case offset printing is the most suitable method of printing but other methods will sufiice. But as the situation of ink drying varies according to the printing method, it is desirable to prepare the ink suited to each printing method. [-5. Drying the Ink Vehicle and oil colors in the ink are separated from each other on the surface of anodic oxidation film, therefore, if left intact the oil colors osmose into pinholes of the anodic oxidation film and the vehicle remains on the surface. But it is desirable to heat and dry in order to improve the dyeing affinity to anodic oxidation film and shorten the working time. The advisable conditions are: under the atmosphere of 80-l20 C. for 10-15 mins. Anyhow it is important to dry it until the ink congeals completely. l-6. Removal of the Anodic Oxidation Film Except Figures Etching aluminum by steeping it for a minute or two in 10 percent sodium hydroxide solution (temperature 80-90 0). As the figures have alkali-proof vehicle adhering on their surfaces they are not acted upon by the etching solution, and the anodic oxidation film except the figures is removed; thus relief figures are presented. I7. Washing Out the Etching Solution Same as l-2. l-8. Neutralization of the Residual Etching Solution Stirring up for l or 2 minutes in 10-15 percent nitric acid solution. l-9. Washing Out the Neutralized Solution Same as [-2. l-lO. Formation of the Anodic Oxidation Film Re-anodic-oxidizing to form anodic oxidation film in the etched part except the figures. In this case, as the surface of the figures is masked by the acid-proof vehicle, it is not acted upon by the electrolyte. Electrolytic conditions are the same as 1-l. [-1 l. Washing Out the Electrolyte Same as l-2. l-l 2. Sealing Pinholes The pinholes of the anodic oxidation film which is formed by re-anodic-oxidizing are sealed by steam treatment. In addition, when coloring the anodic oxidation film, it must be dyed with water paint before this sealing treatment. l-l 3. Removal of the Vehicle In order to remove the vehicle adhering to the anodic oxidation film of aluminum, there are two processes-mechanical and chemical. It is desirable to treat chemically; for example, in aqueous solution containing precipitated calcium carbonate. ll 4. Washing Out the Vehicle Solution Same as l-2. This is not necessary if the vehicle is removed mechanically. 1- l 5. Sealing the Pinholes The part of figures from which the vehicle is removed absorbs oil colors in its pinholes, and if the pinholes are sealed, the colors settle completely. This treatment is completed by immersing for 10 minutes in steam of about three atmospheric pressures. (Example 2. In Case of Forming the Aluminum Figure Patterns on the Surface of a Material) (See FIG. 2.) 2-1. Sticking Aluminum Foils Sticking an aluminum foil on the surface of the material. The thickness of the foil is not especially limited but, for example, 0.05-0.08 mm. is desirable. When sticking it is necessary that the adhesive is acidand alkali-proof; therefore the one made of rubberlike materials or synthetic resins is desirable. 2-2. Formation of the Anodic Oxidation Film Same as l- 1. 2-3. Washing Out the Electrolyte Same as l-2. 2-4. Dehydration Same as I-3. 2-5. Printing the Figures Same as l-4. 2-6. Drying the Ink Same as 1-5. It may be processed at low temperature, if the material cannot bear high temperature. 2-7. Removal of the Aluminum Foil Except the Figures Same as I-6. When the aluminum foil is thick, the treatment time may be lengthened or aluminum surface may be reetched. 2-8. Washing Out Etching Solution Same as I-2. 2-9. Neutralization of the Residual Etching Solution Same as l-8. 2-l0. Washing Out the Neutralized Solution Same as 1-9. 2-1 1. Removal of the Vehicle Same as l-l3. 2-l2. Washing Out the Vehicle Solution Same as l-I4. 2-I 3. Sealing of the Pinholes Same as l-l 5.

I claim:

1. A method of aluminum processing, comprising the steps of anodizing an aluminum body having an exposed surface for fonning on the latter a porous anodic layer; producing on said layer at least one figure with an ink comprising an organic pigment and an alkaliand acid-resistant vehicle selected from the group composed of rubber and natural and synthetic resins; allowing the pigment to sediment into the pores of said layer while the vehicle is retained on and covers portions of the layer which correspond to the figure; steeping the aluminum body in an etching solution to etch the exposed surface where the latter is not covered by the retained vehicle, thereby leaving a colored figure in relief corresponding to the covered portions; and removing the retained vehicle from the previously covered portions of said layer.

2. A method as defined in claim 1, wherein said vehicle is predominantly composed of rubber.

3. A method as defined in claim 1, wherein said vehicle is predominantly composed of synthetic resin material.

4. A method as defined in claim 1, said organic pigment comprising oil colors.

5. A method as defined in claim 1, wherein said aluminum body is an aluminum foil; and further comprising the steps of bonding the aluminum foil to a surface of an article of material resistant to acid and alkali prior to anodizing; and steeping the article with the anodized aluminum foil in an etching solution until said aluminum foil is completely removed except for said figure.

6. A method as defined in claim 5. wherein said article is a coating on an object which is not resistant to acid and alkali.

7. A method of aluminum processing, comprising the steps of bonding an aluminum foil to a surface of an article which is resistant to acid and alkali at least at such surface; anodizing the aluminum foil and forming on the same a porous anodic layer; producing on said layer at least one figure with an ink comprising an organic pigment and an alkaliand acid-resistant vehicle; selected from the group composed of rubber and natural and synthetic resins; allowing the pigment to sediment into the pores of said layer while the vehicle is retained on and covers portions of the layer which correspond to the figure; steeping the article and aluminum foil in an etching solution to remove the aluminum foil completely except for the portions of said layer covered by the retained vehicle, thereby leaving on said surface of said article a colored figure in relief; and removing the retained vehicle. 

2. A method as defined in claim 1, wherein said vehicle is predominantly composed of rubber.
 3. A method as defined in claim 1, wherein said vehicle is predominantly composed of synthetic resin material.
 4. A method as defined in claim 1, said organic pigment comprising oil colors.
 5. A method as defined in claim 1, wherein said aluminum body is an aluminum foil; and further comprising the steps of bonding the aluminum foil to a surface of an article of material resistant to acid and alkali prior to anodizing; and steeping the article with the anodized aluminum foil in an etching solution until said aluminum foil is completely removed except for said figure.
 6. A method as defined in claim 5, wherein said article is a coating on an object which is not resistant to acid and alkali.
 7. A method of aluminum processing, comprising the steps of bonding an aluminum foil to a surface of an article which is resistant to acid and alkali at least at such surface; anodizing the aluminum foil and forming on the same a porous anodic layer; producing on said layer at least one figure with an ink comprising an organic pigment and an alkali- and acid-resistant vehicle; selected from the group composed of rubber and natural and synthetic resins; allowing the pigment to sediment into the pores of said layer while the vehicle is retained on and covers portions of the layer which correspond to the figure; steeping the article and aluminum foil in an etching solution to remove the aluminum foil completely except for the portions of said layer covered by the retained vehicle, thereby leaving on said surface of said article a colored figure in relief; and removing the retained vehicle. 